Copy vs move
Copy duplicates entries to another day and time, leaving the originals in place — for eating the same thing again. Move relocates them — for food that was logged to the wrong time or day.
Copying a whole meal
Tap the copy icon in the meal's hour header, pick the destination day and time, and every entry in that meal is duplicated there — with the exact servings and units of the original. The icon appears when you are viewing a day other than today, which is when copying a whole meal forward is what you want.
Copying or moving a selection
Tap an entry to start selecting, mark any combination of entries (across meals, if you want), and use Copy or Move from the selection bar. The same destination picker appears; confirm and you're done.
Copies are faithful: the serving snapshot travels, and an entry logged from a photo keeps its photo attached.
A habit worth knowing
There's no single "repeat yesterday" button — but copying yesterday's biggest meal into today, then adjusting one or two entries, is usually faster than re-logging. And for a meal you copy week after week, saving it as a meal turns it into one tap forever.